Enterobacteriaceae

Question 1

What is Enterobacteriaceae?

Answer 1

a phylogenetic grouping including foodborne members Shigella, E. coli, Salmonella, and Yersinia, and opportunistic pathogens Klebsiella, Enterobacter, Serratia, Proteus, Providencia, and Morganella

Question 2

What are the defining features of the group?

Answer 2

Gram (-)
Non-sporulating
straight rods 
facultative anaerobes
catalase (+)
oxidase (-)
glucose fermenters

Question 3

What are the foodborne members of the group?

Answer 3

Shigella, E. Coli, Salmonella, and Yersinina

Question 4

What are the opportunistic pathogens in the group?

Answer 4

Klebsiella, Serratia, Enterobacter, Proteus, Providencia, and Morganella

Question 5

What is another key feature that defines their pathogenicity? Why?

Answer 5

Promisicuous to new DNA (like plasmids)–>new virulence factors and antibiotic resistances

Question 6

What is a major problem for the whole group?

Answer 6

extreme antiobiotic resistance

Question 7

How does antimicrobial sensitivity testing work?

Answer 7

smear agar on plate with liquid culture from patient isolate

place disks of various antibiotics on the plate before overnight incubation

successful plating produces lawn of bacteria interrupted by zones of clearing around antibiotics, which are compared to table of standards

Question 8

What are the important virulence factors in the gut?

Answer 8

pili and type 3 secretions systems

Question 9

Why do gut bacteria need pili?

Answer 9

for attachment, gut and UT constantly push contents out unless they are anchored

Question 10

Why do gut bacteria need T3SS?

Answer 10

adhesion, enterotoxins, and subversion of the gut macrophages

Question 11

What is the major mechanism for enterobacteriacaeae infection?

Answer 11

sampled by M cells in Peyer’s patches–>alter the local macrophages for bacterial survival–>spread to exterior surface of the gut–>goes backward and sideways to affect neighboring cells, local infection

Question 12

Which bacteria infect primarily by backtracking in neighboring cells?

Answer 12

Shigella, E. Coli,

Question 13

What bacteria can use macrophages as trojan horses? What does each cause?

Answer 13

locally: Y. enterocolicita–>false appendicitis
systemtically: Salmonella typhi–>typhoid fever

Question 14

What is meant by using macrophages as trojan horses?

Answer 14

Some bacteria can hijack macrophages to travel to and invade either local or systemic lymph nodes

Question 15

How are the foodborne Enterobacteriaceae transmitted? What can be done to prevent infections?

Answer 15

fecal-oral; water treatment, handwashing, food pasteurization, and cooking

Question 16

What is HUS? What infections cause it and who primarily suffers from it?

Answer 16

Hemolytic-Uremic sundrome, caused by shigella or EHEC infections (resulting from release of shiga toxin in blood)
primarily pediatric with a 5-10% mortality rate

Question 17

What is one of the diagnostic tools for HUS?

Answer 17

Schistocytes present in blood smear

Question 18

What patients develop reactive arthritis?

Answer 18

THose positive for HLA (human leukocyte antigen)-B27

Question 19

What is reactive arthritis and who is typically at risk for developing it?

Answer 19

It is a triad of symptoms–>conjuctivitis, arthritis, and urethritis; usually poor, indigent homeles, old, drunk men get this disease

Question 20

What pathogens result in reactive arthritis?

Answer 20

Shigella, Salmonella, Yersinia, Campylobacter, or chlamydia

Question 21

What is meant by “ICU bugs”?

Answer 21

These are major opportunistic nocosomial pathogens

Question 22

What are the major ICU bugs?

Answer 22

Klebsiella, morganella, providencia, porteus, and serratia

Question 23

Why are ICU bugs important?

Answer 23

They seldom cause symptoms in people that are healthy, but are difficult to treat once introduced by catether, or wound infection or general debilitation

Question 24

What is the best defense against ICU bugs?

Answer 24

frequent changing of IV lines, catheters, ICU and patient scrubdowns, and minimization of hospital stays